Stress-Corrosion Cracking of a Stainless Steel Wire-Rope Terminal

An AISI type 303(Se) stainless steel eye terminal that was roll swaged on the end of a 9.5 mm diam wire rope cracked extensively after one year of service. A hairline crack that had initiated at the inner surface of the fitting was revealed by metallographic examination of a sectioned terminal specimen. It was indicated by the holes in the region adjoining the crack and rough texture of the crack surface that a corrosive medium (presumably seawater) had entered the crack from the inner surface of the fitting and coupled with the hairline crack to develop crevice corrosion. The crack propagated toward the outer surface due to high residual stresses in the swaged metal and was followed closely by corrosion. Stress corrosion as result of a combination of residual stresses plus load stress and corrosion was found to cause the failure. Rotary swaging or swaging in a punch press was recommended instead of roll swaging as they made deformation more symmetrical.